1. Field of the Invention
The invention pertains to shoe inserts, and more particularly to protective shoe inserts.
2. Background Information
Laborers, technicians, supervisors, project managers and other professionals in industrial and construction industries often work in hazardous environments. Job sites and facilities are generally not open to the public and such facilities are not continually cleaned and made safe of dangerous conditions. As such, shards of glass, shreds of metal and other rigid construction materials, in particular nails, pose a continuing threat of injury to the feet of workers in these environments.
To overcome such hazards, it has been proposed, and it is commonly practiced, that the sole of a work boot or safety shoe be integrally constructed of multiple layers of a high tensile strength synthetic or polymeric fibers, such as Kevlar (™) In work boots. U.S. Pat. No. 5,996,225, issued to George Ventura, shows such a technique. Drawbacks, however, to this technique include that it adds cost and complexity to the design of a work boot insole. A similar solution is proposed in U.S. Pat. No. 5,285,583, by Albertus A. W. Alven, of Markdale, Canada, as well in a series of U.S. Patents authored by L. P. Frieder et al., for instance U.S. Pat. Nos. 2,803,895, 2,808,663, and 2,920,008. Each of these patents teach that multiple stacked, resin-impregnated, fibrous laminates are needed to prevent penetration by sharp objects.
While also an integrally fabricated portion of the protective footwear sole, U.S. Pat. No. 4,271,607, issued to Herbert Funck of Germany, shows that a two-part, yet single-layered, prefabricated steel inlay can be used as a protective shield.
Because the metal inlay is integrally molded into the footwear sole, there is the risk that movement and flexing on the integral and flexing will damage the interior lining and sole of the protective footwear. Appreciating this problem Funck, requires a grove and two-part lip molding combination in the forward end (toe end) of the sole to prevent movement, and a cup shaped holder secured to the underside of the steel inlay at the rear end (heel end) to facilitate alignment within the sole assembly. A further drawback is that by incorporating the metal inlay into the sole of the footwear, only about 80% of the bottom surface of a foot is protected by the metal inlay.
While either a separate insole insert for footwear, or an integrally molded part at manufacture, U.S. Pat. No. 6,178,664, issued to Robert D. Yant et al., the '664 patent shows another multi-layered metal sheet assembly designed to protect the sole of a shoe from puncture by a sharp object.
As is the case with other multi-layered protective layer assemblies, the '664 patent requires an intricate manufacturing process, involving the stamping of multiple metal sheets and spot welding each metal sheet to the next. The end result of the '664 patent being a variable thickness, multi-layered metal sheet assembly.